Measurement system with detection mechanism and method of operation thereof

An embodiment of the present invention relates generally to a measurement system, and more particularly to a system with a detection mechanism.

In the field of microscopy and material characterization, atomic force microscopy (AFM) and related techniques such as Scanning Microwave Impedance Microscopy (SMIM) can be used to measure surface features and electrical responses of materials. These methods are applied in areas including semiconductor research, materials development, and biological studies to obtain information about physical and electrical characteristics of a sample.

Thus, a need still remains for a measurement system with detection mechanisms that delivers high spatial resolution together with stable, quantitative performance across multiple imaging modes and a range of materials. In view of the ever-increasing commercial competitive pressures, along with growing manufacturing needs, manufacturing expectations, and the diminishing opportunities for meaningful product differentiation in the marketplace, it is increasingly critical that answers be found to these problems. Additionally, the need to reduce costs, improve efficiencies and performance, and meet competitive pressures adds an even greater urgency to the critical necessity for finding answers to these problems.

Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.

An embodiment of the present invention provides a measurement system including: an impedance detection unit configured to: capture a probe measurement associated with a key, where the probe measurement is a first response or a second response based on a first microwave excitation or a second microwave excitation, respectively; generate a first channel voltage or a second channel voltage based on the first response or the second response, respectively; determine a phase offset based on the first channel voltage; store the phase offset associated with the key; and calibrate the probe measurement by adjusting a phase based on computation of the second channel voltage with the phase offset accessed by the key.

An embodiment of the present invention provides a method of operation of a measurement system including: capturing a probe measurement associated with a key, where the probe measurement is a first response or a second response based on a first microwave excitation or a second microwave excitation, respectively; generating a first channel voltage or a second channel voltage based on the first response or the second response, respectively; determining a phase offset based on the first channel voltage; storing the phase offset associated with the key; and calibrating the probe measurement by adjusting a phase based on computation of the second channel voltage with the phase offset accessed by the key.

An embodiment of the present invention provides a non-transitory computer-readable medium storing an instruction that, when executed by a control circuit of a measurement system, causes the control circuit to perform functions including: capturing a probe measurement associated with a key, where the probe measurement is a first response or a second response based on a first microwave excitation or a second microwave excitation, respectively; generating a first channel voltage or a second channel voltage based on the first response or the second response, respectively; determining a phase offset based on the first channel voltage; storing the phase offset associated with the key; and calibrating the probe measurement by adjusting a phase based on computation of the second channel voltage with the phase offset accessed by the key.

Certain embodiments of the invention have other steps or elements in addition to or in place of those mentioned above. The steps or elements will become apparent to those skilled in the art from a reading of the following detailed description when taken with reference to the accompanying drawings.

Description of various embodiments of the present invention is described with an example of development of an atomic force microscope (AFM) system incorporating a Scanning Microwave Impedance Microscopy (SMIM) module that implements phase calibration with a probe configured to detect mechanical and microwave responses of a sample.

The following embodiments are described in sufficient detail to enable those skilled in the art to make and use the invention. It is to be understood that other embodiments would be evident based on the present disclosure, and that system, process, or mechanical changes may be made without departing from the scope of an embodiment of the present invention.

In the following description, numerous specific details are given to provide a thorough understanding of the invention. However, it will be apparent that the invention may be practiced without these specific details. In order to avoid obscuring an embodiment of the present invention, certain circuits, system configurations, and process steps are not disclosed in detail.

The drawings showing embodiments of the system are semi-diagrammatic, and not to scale and, particularly, some of the dimensions are for the clarity of presentation and are shown exaggerated in the drawing figures. Similarly, although the views in the drawings for ease of description generally show similar orientations, this depiction in the figures is arbitrary for the most part. Generally, the invention can be operated in any orientation. The embodiments of various components as a matter of descriptive convenience and are not intended to have any other significance or provide limitations for an embodiment of the present invention.

The embodiments can be numbered as first embodiment, second embodiment, etc. or can be described without a numeric designation as a matter of descriptive convenience and are not intended to have any other significance or provide limitations for an embodiment of the present invention. The terms first, second, etc. or without a numeric designation can be used throughout as part of element names and are used as a matter of descriptive convenience and are not intended to have any other significance or provide limitations for an embodiment.

The term “module” or “unit” or “circuit” or “mechanism” referred to herein can include or be implemented as or include software running on specialized hardware, hardware, or a combination thereof in the present invention in accordance with the context in which the term is used. For example, the software can provide instructions and can be implemented as machine code, firmware, embedded code, and application software. The software can also include a function, a call to a function, a code block, or a combination thereof.

Also, for example, the hardware can be gates, circuitry, processor, computer, integrated circuit, integrated circuit cores, memory devices, a pressure sensor, an inertial sensor, a microelectromechanical system (MEMS), passive devices, physical non-transitory memory medium including instructions for performing the software function, a portion therein, or a combination thereof to control one or more of the hardware units or circuits. Further, if a “unit” or a “circuit” is written in the claims section below, the “unit” or the “circuit” is deemed to include hardware circuitry for the purposes and the scope of the claims.

For example, the hardware can include an atomic force microscope (AFM) head assembly, cantilevers or probes with conductive or metal-coated tips, piezoelectric scanners for positioning and feedback control, microwave transmission lines or coaxial feed structures for signal delivery, impedance-matching networks, microwave sources and detectors, low-noise amplifiers, mixers, and demodulators for signal processing, or a combination thereof.

Also for example, the hardware can include vibration-isolation platforms, environmental enclosures, signal-conditioning circuits, controller and feedback electronics, lock-in amplifiers, data-acquisition units, or other components for AFM and Scanning Microwave Impedance Microscopy (SMIM) measurements, or a combination thereof.

As a specific example, the excitation sources can include microwave signal generators, vector network analyzers (VNAs), or frequency synthesizers configured to provide continuous-wave or modulated microwave excitations, impedance-matched through transmission lines or couplers to the probe. As another specific example, the excitation sources can include broadband microwave sources, mixers, or oscillators configured for amplitude or frequency modulation, phase control, or impedance calibration, any other microwave excitation sources, or a combination thereof.

The module, units, circuits, or mechanism in the following description of the embodiments can be coupled or attached to one another as described or as shown, as examples. The coupling or attachment can be direct or indirect without or with intervening items between coupled or attached modules or units or circuits or mechanisms. The coupling or attachment can be by physical contact or by communication between modules or units or circuits or mechanisms, such as wireless communication.

It is also understood that the nouns or elements in the embodiments can be described as a singular instance. It is understood that the usage of singular is not limited to singular but the singular usage can be applicable to multiple instances for any particular noun or element in the application. The numerous instances can be the same or similar or can be different.

Referring now to, therein is shown an example of a system architectural diagram of a measurement systemwith a detection mechanismin an embodiment of the present invention. One or more embodiments address measurement functions of the measurement systemas a distributed platform in which exchanges of commands and data with a detection mechanismacross a network topology. One or more embodiments address AFM and Scanning Microwave Impedance Microscopy (SMIM) measurement functions of the measurement systemas a distributed platform in which commands and data are exchanged among the first device, the second device, the detection mechanism, or a combination thereof over the network.

The measurement systemcan include a first device, such as a client or a server, connected to a second device, such as a client or server. The first devicecan communicate with the second devicethrough a network, such as a wireless or wired network. For example, the first devicethat implements the AFM/SMIM instrument and a local controller is connected to the second device.

For example, the first devicecan be of any of a variety of computing devices, such as a measurement equipment, a computer, a notebook computer, or other multi-functional device. Also, for example, the first devicecan be included in a device or a sub-system. As a specific example, the first devicecan be an atomic force microscope (AFM) including a Scanning Microwave Impedance Microscopy (SMIM) module or any other scanning probe microscopy instrument.

For example, the first devicecan function as an atomic force microscope (AFM).

As an example, the first devicepositions a probe or cantilever tip near or in contact with a sample, measures the interaction forces between the probe and the sample, and detects corresponding deflection or response signals. In an embodiment, the first deviceincludes a SMIM circuit coupled to the probe to apply a microwave excitation to the sampleand detect the reflected or transmitted microwave signal from a tip-sample interaction. Also for example, the collected signals can include mechanical response data, SMIM baseband channels (e.g., in-phase and quadrature or capacitance and conductance), impedance data, or a combination thereof, which are processed to produce maps of topography, permittivity, conductivity, or other electrical or material parameters of the sample. As an example, data acquisition and image formation can be performed during contact or non-contact scanning modes including off-resonance tapping and/or lift-mode passes. As another example, the second devicecan perform impedance extraction, data reconstruction, calibration (including phase calibration in SMIM), or analysis using signal-processing algorithms, artificial intelligence (AI) models, machine-learning models, or other computational techniques

For example, the usersupplies the sampleto the first devicewith the detection mechanism, and the first devicecaptures response signals from the sampleand processes data generated from the signals. The detection mechanismincludes AFM scanner and probe-control electronics, feedback circuitry, and SMIM microwave excitation and demodulation circuitry to drive a probe with a mechanical and microwave excitation, detecting responses corresponding to tip-sample interactions, and analyzing the detected responses to determine material and electrical information of the sample. As another example, the first devicecan perform all computations locally or, via the network, off-load part of the computation workload or share the local computation results with the second devicewith a higher processing capacity for additional processing and storage, including phase calibration and impedance-map generation.

For illustrative purposes, the sampleis shown in the detection mechanism, although it is understood that the samplecan be outside of the detection mechanism.

For example, the samplecan be mounted on a stage or chuck of the AFM with a SMIM module or SMIM system and provided to the first deviceto be characterized or tested.

For illustrative purposes, the detection mechanismis shown in the first device, although it is understood that the detection mechanismcan be implemented in a different manner. For example, the detection mechanismcan be distributed between the first deviceand the second device. Also for example, the first devicecan include multiple probes and/or multiple instruments that independently operate AFM or SMIM probes for parallel measurements across multiple samples, and the collected information for all of the samplescan be transferred to the second devicefor combined analysis or comparison.

The first devicecan couple, either directly or indirectly, to the networkto communicate with the second deviceor can be a stand-alone device. The first devicecan further be separated from or incorporated with a smart phone, a tablet computer, a desktop, a laptop computer, a scanner, or other personal electronic devices or can include an embedded controller within the instrument chassis.

The second devicecan be any of a variety of centralized or decentralized computing devices. For example, the second devicecan be a computer, workstation, server, grid computing resources, a virtualized computer resource, cloud computing resource, routers, switches, peer-to-peer distributed computing devices, or a combination thereof. In an embodiment, the second devicecan execute image-processing, impedance-mapping, phase calibration, or data-classification software for AFM or SMIM datasets.

The second devicecan be centralized in a single room, distributed across different rooms, distributed across different geographical locations, embedded within a telecommunications network, on-premises, or remote. The second devicecan couple with the networkto communicate with the first device. The second devicecan also be a client type device as described for the first device. For example, the second devicecan receive the SMIM baseband data or AFM deflection signals and perform advanced analysis, visualization, or data storage.

Also, for illustrative purposes, the measurement systemis described with the second deviceas a computing device, although it is understood that the second devicecan be different types of devices. Also, for illustrative purposes, the measurement systemis shown with the second deviceand the first deviceas endpoints of the network, although it is understood that the measurement systemcan include a different partition between the first device, the second device, and the network. For example, the first device, the second device, or a combination thereof can also function as part of the networkand host services for instrument control, data streaming, and user interfaces.

The networkcan span and represent a variety of networks. For example, the networkcan include wireless communication, wired communication, optical, ultrasonic, or the combination thereof. Satellite communication, cellular communication, Bluetooth, Infrared Data Association standard (IrDA), wireless fidelity (WiFi), and worldwide interoperability for microwave access (WiMAX) are examples of wireless communication that can be included in the communication path. Ethernet, digital subscriber line (DSL), fiber to the home (FTTH), and plain old telephone service (POTS) are examples of wired communication that can be included in the network. Further, the networkcan traverse a number of network topologies and distances. For example, the networkcan include direct connection, personal area network (PAN), local area network (LAN), metropolitan area network (MAN), wide area network (WAN), or a combination thereof.

For example, a usercan utilize the first deviceto initiate or supervise a measurement sequence of a sample, while the second devicecan receive sensed measurement information, execute analytical routines, and return processed measurement information to the user. As an example, the usercan be an operator, a laboratory technician, an engineer, a scientist, or any other users of the measurement system. Also as an example, the second devicecan be implemented as centralized or decentralized computing resources. This partition of control and computation can allow AFM and SMIM measurements to be performed locally while remote or higher-level devices perform impedance analysis, calibration, device health monitoring, or visualization of results.

For example, the second devicecan host portions of the detection mechanismfor executing the analytical routines using the sensed measurement information. As an example, the detection mechanismcan include a probe control circuit, feedback electronics, and SMIM detection circuitry including microwave excitation, quadrature demodulation, and impedance-analysis components. Further details for operations, components, and technical aspects of the detection mechanismwill be described below in the description of the measurement system.

Referring now to, therein is shown an example of a block diagram of the detection mechanismoperating within the measurement systemof. The detection mechanismcan include an excitation unit, a probe, a sample, and an impedance detection unitthat are electrically or functionally coupled together for performing measurement operations. The detection mechanismcan implement phase calibration in SMIM, in which the impedance detection unitdetermines a system phase offset from a first channel voltage, stores the system phase offset in a memory under a key associated with probe and excitation settings, and applies the stored system phase offset to subsequent channel voltages in real time to generate phase-corrected SMIM images. Phase calibration can be performed at a single user-selected point, either in air or at an approached Z position, and the captured phase at that point is stored as the system phase offset keyed to probe or frequency for real-time subtraction during measurement.

For example, generation of phase-corrected SMIM images in real time refers to processing with deterministic, bounded latency (e.g., with a configurable maximum delay) so that a computed result is available during an ongoing acquisition rather than deferred to offline or batch processing. In an AFM/SMIM context, the real time processing can indicate that calibration and image updates are completed within the dwell time of the current acquisition cycle before the next acquisition cycle begins.

By way of an example, the excitation unitis an electronic module configured to generate a controlled microwave excitation and to deliver the microwave excitation to the probe, including a first microwave excitationand a second microwave excitation. By way of an example, the probeis a scanning probe assembly configured to apply the microwave excitation to the sampleand to sense corresponding mechanical responses, microwave responses, or a combination thereof from a tip-sample interaction. The probecan include an AFM cantilever with a conductive or metal-coated tip.

By way of an example, the impedance detection unitis a signal-processing module configured to receive mechanical responses, microwave responses, or a combination thereof from the probe. The impedance detection unitcan generate conditioned baseband channel voltages, including a first channel voltageand a second channel voltage, that represent impedance-related properties of the sample. The impedance detection unitcan include demodulation, filtering, amplification stages, or a combination thereof for generating conditioned baseband channel voltages.

The impedance detection unitcan include a quadrature demodulation unitand an operational configuration unit. By way of an example, the quadrature demodulation unitis a circuit configured to multiply the microwave response by phase-coherent reference signals to produce in-phase and quadrature (I/Q) baseband components (or equivalent capacitance/conductance channels) for further conditioning. By way of an example, the operational configuration unitis a digital control module configured to orchestrate scanning and timing, coordinate the excitation unitand the impedance detection unit, command constant frequency/power settings, execute phase calibration in real time, or a combination thereof. This digital phase-calibration flow does not use an analog phase shifter and does not require scanning or Z-sweeping to establish the phase offset computed from I/Q and then subtracted in real time. By eliminating the analog phase shifter, the measurement systemavoids the RF-bandwidth limitations of active shifters and the usability constraints of passive, knob-adjusted shifters.

It has been discovered that the quadrature demodulation unitand the operational configuration unitcan execute SMIM phase calibration digitally. The quadrature demodulation unitcan provide in-phase and quadrature voltages, and the operational configuration unitcan compute a magnitudeand an uncalibrated phase, determine and store a one-time system phase offset, and subtract the stored phase offsetin real time via the key, thereby eliminating analog phase-shifter adjustments, reducing setup time, and broadening usable RF bandwidth.

The probecan interact with the samplemechanically while receiving microwave energy from the excitation unitand returning a microwave response that encodes the local impedance at the tip-sample junction. The probecan capture a probe measurementincluding a first responseduring application of the first microwave excitationand a second responseduring application of the second microwave excitation. By way of an example, the first responseand the second responseare microwave signals that have been altered by the tip-sample interaction. By way of an example, the probe measurementis an electrical response derived from the probe.

The quadrature demodulation unitcan perform signal mixing between the first response, the second response, or a combination thereof and reference signals that have predetermined amplitude and phase relationships. The first response, the second response, or a combination thereof can be multiplied by phase-coherent in-phase and quadrature (I/Q) reference signals in the quadrature demodulation unitto translate signals from the microwave carrier to baseband.

The probecan provide the probe measurementto the quadrature demodulation unitfor downstream processing by the impedance detection unit. The probe measurementcan include a voltage proportional to a reflected or transmitted microwave signal that represents local sample properties sensed at a tip-sample junction between a tip of the probeand the sample.

The quadrature demodulation unitcan convert the microwave responses from the probeinto baseband electrical signals for analysis and imaging. The quadrature demodulation unitcan generate a first channel voltagebased on the first responseand can generate a second channel voltagebased on the second response. By way of an example, the first channel voltageand the second channel voltageare baseband signals produced after demodulating the microwave responses to obtain information that correlates with local capacitance and conductance of the sample. The first channel voltagecan include a first in-phase voltageand a first quadrature voltage. The second channel voltagecan include a second in-phase voltageand a second quadrature voltage. For example, in-phase and quadrature voltages are two perpendicular measurements of the same signal that are 90° apart, which are used to compute amplitude and phase.

The impedance detection unitcan be implemented using resistor-capacitor (RC) circuit networks at one or more stages to realize time constants that set demodulation bandwidth, noise filtering, and output shaping. By way of an example, an RC network is a combination of resistors and capacitors that creates a time constant τ=R×C used to establish a cutoff frequency, integrate or differentiate a signal, or introduce a controlled phase shift.

The quadrature demodulation unitcan include RC networks at the mixer outputs to form baseband smoothing/anti-alias filters and, in analog-reference embodiments, can include RC all-pass phase-shift networks to generate or trim the in-phase and 90-degree quadrature references. The mixing element (e.g., a chopper/switching mixer or analog multiplier) can be active, while the immediate post-mixer low-pass sections can be implemented with RC networks to remove residual carrier and high-frequency products before further conditioning.

The operational configuration unitcan perform phase calibration in SMIM to correct system-induced phase effects. The operational configuration unitcan determine a phase offsetbased on the first in-phase voltageand the first quadrature voltageand can store the phase offsetassociated with a key. By way of an example, the phase offsetis a calibration angle representing a phase shift. By way of an example, the keyis an identifier used to retrieve a calibration value such as the stored phase offset. The operational configuration unitcan then calibrate the probe measurementby adjusting a phasebased on computation of the second in-phase voltageand the second quadrature voltagewith the stored phase offsetaccessed via the key.

The operational configuration unitcan form the keybased on identifiers of the current configuration, including a probe identifierand an excitation frequency identifier. For example, the operational configuration unituses the probe identifier, the excitation frequency identifier, or a combination thereof as inputs to construct the keythat indexes and retrieves the stored phase offsetfrom a memory (e.g., volatile, non-volatile, persistent memory, etc.) for the present probe and frequency. By way of an example, the probe identifieris a label that identifies the probe. By way of an example, the excitation frequency identifieris a label that identifies the drive frequency of the microwave excitation for the current measurement.